Compositions and methods for inhibition of phospholipase a2 mediated inflammation

ABSTRACT

Specific, highly potent 2-oxo-amide based inhibitors of phospholipase A 2  (PLA 2 ) activity are provided. A role for PLA 2  activity in spinally mediated inflammatory processes is established, and a method for treating hyperalgesia and other inflammatory conditions associated with PLA 2  activity is provided.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application claims the priority of U.S. Provisional Patent Application No. 60/362,701, filed on Mar. 7, 2002.

FIELD OF THE INVENTION

The present invention relates generally to the field of non-steroidal anti-inflammatory agents for inhibition of phospholipase A2 enzymes, and the use of such agents in controlling inflammation.

BACKGROUND OF THE INVENTION

Injury to one part of the body often results in hypersensitivity to painful stimuli. It has recently been discovered that this phenomenon is not, as previously thought, driven only by transmission of nerve impulses from a site of peripheral inflammation through the spinal cord to the brain. Rather, Samad, et al. have opined that hyperalgesia results from facilitation of pain processing signals inside the brain and spinal cord. Samad, et al., Nature 410, 471-475 (2001).

One theory as to how such signalling occurs posits that an increase in cerebrospinal levels of interleukin-1β may signal the central nervous system that an injury to the body has occurred. Eck, et al. have suggested that interleukin-1β may interact with cells at the blood-brain barrier to stimulate expression of cyclooxygenase-2 and prostaglandin E synthase. Eck, Nature 410: 430-431 (2001).

Following hydrolysis of arachidonic acid from phospholipid by phospholipase A₂, cyclooxygenase-2 converts arachidonic acid into prostaglandin H₂. In turn, prostaglandin E synthase converts prostaglandin H₂ into prostaglandin E₂, a potent inflammatory mediator. Prostaglandin E₂ also activates the synthesis of interleukin-1β by microglia (possibly explaining the latter's presence in cerebrospinal fluid). Whatever the specific mechanism, the end product of the central cyclooxygenase signaling cascade is enhanced pain and inflammation.

To date, therapeutic proposals to target the cyclooxygenase signalling cascade to treat hyperalgesia have focused on inhibition of cyclooxygenase-2 activity. See, e.g., Bartfai, T., Nature 410: 425-427 (2001); referencing Samad, et al. and Eck, supra. However, current pain remedies and anti-inflammatories commonly employed to this end are either potentially addictive opiates or are non-steroidal anti-inflammatories (NSAIDS) designed to target the cyclooxygenase enzymes (e.g., aspirin, ibuprofen, ketorolac, Celebrex™ and Vioxx™). Cyclooxygenase-2 is also the target of most antipyretic (fever-reducing) drugs.

Phospholipase A₂ (PLA₂) has not received much attention as a therapeutic target in the cyclooxygenase signaling cascade. To the contrary, it has been reported that no increase in PLA₂ activity in the spinal cord or brain is produced in response to peripheral injury in an animal model (rat paw edema). See, e.g., Samad, et al., at 471 and 473, FIG. 2, which recently concluded that “COX-2 [cyclooxygenase-2] alone appears to be pivotal in central [nervous system] PGE₂ induction.” Id., at 471.

SUMMARY OF THE INVENTION

The invention provides potent inhibitors of phospholipase A₂ (PLA₂), and methods for use of the inhibitory compounds. In the latter respect, it has been discovered that PLA₂ is both present and active in the spinal cord. In particular, it is causatively related to spinally mediated inflammatory processes, suggesting a new method for treating inflammation, pain, hyperalgesia (pain experienced through hypersensitivity to stimulus), and other conditions causatively related to inflammation (e.g., neurological disorders stemming from inflammation affecting the central nervous system (CNS)). The inhibitory compounds of the invention are especially useful in treating these conditions, and act on PLA₂ rather than on the cyclooxygenase enzymes.

The PLA₂ inhibitors of the invention are 2-oxoamide compounds, including compounds which exhibit a high degree of specificity for particular isoforms of PLA₂, such as the cytosolic (cPLA₂) and calcium-independent (iPLA₂) isoforms of the molecule, one or both of which are present in many different cell types. At dosages well below cytotoxic levels, the PLA₂ inhibitors can completely abrogate prostaglandin production (induced, in experimental models, by LPS). Thus, the PLA₂ inhibitors of the invention are especially useful agents for treating inflammation, pain and hyperalgesia.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1. Thermal escape latency (PWL) plotted versus time after injection of carrageenan into plantar face of left hind paw of rats pretreated (−10 mm) with intrathecal (IT) PLA₂ inhibitors, as follows: A: arachidonoyl trifluoromethylketone (AATFMK) (200 μg; closed diamonds and 100 μg; open triangles) and C: methyl arachidonyl fluorophosphonate (MAFP) (300 μg; closed circle and 100 μg; open triangles). The control group received paw carrageenan and IT vehicle. The paw withdrawal latency (PWL) for the inflamed paw (ipsi, closed squares) and non-inflamed paw (contra, open squares) is shown. Hyperalgesic index calculated over time from T=0 to T=180 min after different doses of IT B: ATFMK and D: MAFP. Each time point and bar represents the average and SEM for 4-6 rats and (*) represents P<0.05 versus vehicle treated carrageenan injected group (ipsilateral paw values).

FIG. 2A) Thermal escape latency (PWL) plotted versus time after injection of carrageenan into plantar face of left hind paw of rats pretreated (−10 min) with intraperitoneal AATFMK (200 μg/0.5 ml, contralateral paw, open triangle; ipsilateral paw, open circles) or vehicle (contralateral paw, closed diamond; ipsilateral paw, closed square). B) Paw height of carrageenan injected (ipsi) and non-treated (contra) hind paws measured at different time points. The control group received IT vehicle and the other group received IT AATFMK (200 μg) ten minutes prior to carrageenan injection. Each time point and bar represent the average and SEM for 4-6 rats.

FIG. 3. Thermal escape latency (PWL) plotted versus time after injection of carrageenan into plantar face of left hind paw of rats posttreated (+180 mm) with IT AATFMK (200 μg) contralateral paw, open square; ipsilateral paw, closed circles. Each time point represents the average and SEM for 4-6 rats.

FIG. 4. Flinching behavior plotted versus time following injection of formalin into the dorsal side of the right hindpaw of rats pretreated (−10 mm) with IT vehicle (open squares) or A: IT AATFMK (200 μg; closed diamonds), or C: IT MAFP (300 μg; closed circle). Cumulative number of flinches during Phase 2 (10-60 mm, total number) observed after different doses of B: IT AATFMK and D: IT MAFP. Each timepoint and bar represents the average and SEM for 4-6 rats and (*) represents P<0.05 versus vehicle treated formalin injected group.

FIG. 5. Q-PCR analysis. A) Expression levels are determined by standard curve method. For each gene expression in control rat spinal cord is compared to expression in spinal cord of rats treated with carrageenan hind paw injection either 2 or 4 hours after injection.

FIG. 6. iPLA₂ protein is expressed in rat lumbar spinal cord. Top: anti-human iPLA₂ antibody, Bottom: β-ctin loading control. Lane (1) ladder, (2-4) control rat, (5-7) 2 hr carrageenan, (8-10) 4 hr carrageenan. No significant increase in activity was observed following carrageenan injection to the hind paw 120 minutes or 240 minutes after injection in comparison with control (0 minutes). Each value is the average of three rats assayed in duplicate.

FIG. 7. Inhibition of spinal iPLA₂ activity in vitro. Rat lumbar spinal cord homogenates were assayed for A: cPLA₂ activity, or B: iPLA₂ activity for one hour in the presence of 0.8 mole % inhibitor. Each value is the average of three rats assayed in duplicate. *P-values are all less than 0.009.

FIG. 8. The activity of cPLA₂ was tested on mixed micelles composed of TX-100 (400 AK, 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (97 μM, 100,000 cpm) and PIP₂ (3 μM, 0.6 mole %). The surface concentration of various inhibitors in the mixed micelles was increased as shown for OA1 (▴), OA4 (▪), and OA7 (□). The data for OA1 and OA4 were fit to a simple logarithmic function (OA1, solid curve and OA4, dashed curve). The X_(I)(50) determined by this fit was 0.017±0.009 for OA1 and 0.009±0.004 for OA4. The data for OA7 were fit to a linear function. The X_(I)(50) for OA7 determined by this fit was 0.068±0.005.

FIG. 9. The relative activity of cPLA₂ was tested on mixed micelles composed of TX-100 (3 mM) and 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (1 mM, 200,000 cpm) with no PIP₂ present. The surface concentration of OA1 was 0 mole fraction (left bar) and 0.01 mole fraction (40 μM, right bar). The data for both bars have been normalized to the control (left bar).

FIG. 10. The activity of cPLA₂ was tested on mixed micelles composed of TX-100 (3 mM) and 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (1 mM, 200,000 cpm) with no PIP₂ present. The surface concentration of OA4 was increased as shown. The curve is a fit of the data to a simple log function. The curve values give an X_(I)(50) of 0.0027±0.0012 mole fraction.

FIG. 11. The activity of cPLA₂ was tested on mixed micelles composed of TX-100 (400 AK, 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (97 μM, 100,000 cpm) and PIP₂ (3 μM, 0.6 mole %). The micelles also contained a final concentration of 0.005 mole fraction of OA1 (20 μM). cPLA₂ was first preincubated with OA1 for the indicated times (at 200 μM) before 10-fold dilution of the enzyme and inhibitor into the substrate-containing solution.

FIG. 12. A) The activity of cPLA₂ was tested on mixed micelles composed of TX-100 (400 μM, 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (97 μM, 100,000 cpm) and PIP₂ (3 μM, 0.6 mole %). The micelles also contained a final concentration of 0.005 mole fraction of OA4 (20 μM). cPLA₂ was first preincubated with OA4 (20 μM) for 0 or 4 hours before it was added to the the substrate-containing solution that also contained OA4 (20 μM). B) The activity of cPLA₂ was tested on mixed micelles composed of TX-100 (400 μM, 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (97 μM, 100,000 cpm) and PIP₂ (3 μM, 0.6 mole %). The micelles also contained a final concentration of 0.005 mole fraction of OA4 (20 μM). cPLA₂ was first preincubated with OA4 (20 μM) for 0 or 4 hours before it was added to the the substrate-containing solution that contained no additional OA4. This resulted in a final concentration for OA4 of 0.0005 mole fraction (2 μM).

FIG. 13. The activity of cPLA2 was tested on mixed micelles composed of TX-100 (400 μM), 1-palmitoyl-2-(1-[¹⁴C])-arachidonoyl PC (97 μM, 100,000 cpm) and PIP₂ (3 μM, 0.6 mole %). The surface concentration of OA10 (▪) and OA11 (□) were separately increased as shown. The data were fit to linear least squares functions (OA10, dashed line and OA11, solid line). The lines give values for the OA11 X_(I)(50) of 0.047±0.006 and for the OA10 X_(I)(50) of 0.045±0.007.

FIG. 14. Varying concentrations of OA1 (▴) or OA4 (▪) were added to P388D₁ cells 30 min. prior to stimulation. The cells were then stimulated with LPS for 1 hour and PAF for 15 min as described. After stimulation, the media was harvested and the PGE₂ levels in the media were quantitated as described. The data were normalized to control DMSO-treated LPS/PAF-stimulated cells to appear as % inhibition. The data points are connected by a dashed line (OA1) and a solid line (OA4) for ease of visualization.

FIG. 15. Varying concentrations of OA1 (▴) or OA4 (▪) were added to P388D₁ cells 30 min. prior to stimulation. The cells were then stimulated with LPS 18 hr as described. After stimulation, the media was harvested and the PGE₂ levels in the media were quantitated as described. The data were normalized to control DMSO-treated LPS-stimulated cells to appear as % inhibition. The lines correspond to a non-linear least squares fit of the data to logarithmic functions (OA1, solid curve and OA4, dashed curve). These functions were then used to calculate the IC₅₀ for OA1 (7.8 μM) and OA4 (5.8 μM).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A. PLA₂ Activity in the Central Nervous System.

The invention provides potent inhibitors of PLA₂, and methods for use of the inhibitory compounds. In the latter respect, it has been discovered that, although mRNA and protein levels of PLA₂ are not detectably upregulated in response to inflammatory signals, PLA₂ is nonetheless active in the spinal cord, and is causatively related to hyperalgesia. Targeting PLA₂ activity thus provides a new method for treating general inflammation and pain, as well as hyperalgesia (pain experienced through hypersensitivity to stimulus).

PLA₂ is the name for the class of lipolytic enzymes that hydrolyze the acyl group from the sn-2 position of glycerophospholipids, generating free fatty acids and lysophospholipids. The phospholipase A₂ superfamily of enzymes consists of two large branches, the histidine and serine PLA₂'s. The histidine PLA₂'s are similar small, secreted, Ca²⁺-dependent enzymes that utilize a nucleophilic water molecule activated by the active site Ca²⁺, aspartates, and especially a catalytic histidine (Groups I-III, V, IX-XIV). The other branch of the superfamily is composed of larger, typically cytosolic enzymes that utilize a nucleophilic serine (Groups IV and VI-VII).

Cytosolic PLA₂ (cPLA₂) has a strong preference for arachidonic acid at the sn-2 position of phospholipids and this observed in vitro preference has been shown to have physiological significance in the release of arachidonic acid and production of prostaglandins in vivo. In contrast, calcium-independent PLA₂ (iPLA₂) has no significant fatty acid specificity and its main function is believed to in membrane remodeling, although it is also believed to play a role both in arachidonic acid release and in leukotriene synthesis.

PLA₂ provides the cyclooxygenase enzymes (COX-1 and COX-2) with arachidonic acid, a required substrate for COX enzyme function in vivo. cPLA₂ is the principal provider of free lysophospholipid and arachidonic acid, the precursors of platelet activating factor (PAF) and eicosanoids, respectively. cPLA₂-stimulated production of arachidonic acid provides an intracellular intermediate for lipopolysaccharide (LPS) mediated production of prostaglandins. In particular, the arachidonic acid can be made directly into PGE₂ or can be used to transcriptionally upregulate the levels of PLA₂ available for production of prostaglandins (such as PGE₂), which serve as mediators of inflammation and pain.

In addition to supplying substrate for the COX-pathway, it has been shown that arachidonic acid liberated by PLA₂ may play additional roles in augmenting nociception. For example, arachidonic acid potentiates NMDA receptor currents and thus amplifies glutamate-mediated increases in intracellular calcium concentration by binding to sites on the NMDA-receptor, or by modifying the receptor's lipid environment. In addition, isoprostanes, a novel class of eicosanoids, are primarily formed by peroxidation of arachidonic acid in a non-COX dependent fashion. Isoprostanes act to sensitize rat sensory neurons thereby reducing mechanical and thermal withdrawal thresholds.

B. Role of PLAN in CNS Mediated Inflammatory Processes

In contrast to current belief in the art, PLA₂ expression in the spinal cord plays a significant role in spinally mediated inflammation, pain and hyperalgesia. Further, inhibition of PLA₂ activity in the CNS significantly decreases hyperalgesic responses in animals (rat paw edema model), and can abrogate production of PGE₂.

Expression of six PLA₂ enzymes, Groups IB, IIA, IIC, IVA, V and VI occurs in the spinal cord (as confirmed by Q-PCR in Example 5). Groups IVA and VI (referred to herein as cPLA₂ and iPLA₂, respectively) are the most highly expressed, showing over a 16-fold expression difference in comparison to the secretory PLA₂s (sPLA₂). Of the sPLA₂s, Group V shows the lowest expression having 200-fold less message than IB, IIA or IIC and fully four orders of magnitude less message than IVA or VI (data not shown).

Neither mRNA nor protein expression appear to be upregulated in response to local inflammation (Example 5); therefore, the major regulation of cPLA₂ activity is believed to be through translocation of the enzyme from the cytosol to the membrane subsequent to increases in intracellular calcium levels rather than through changes in protein expression. In addition to activation through translocation, cPLA₂ activity has also been shown to increase modestly following phosphorylation by MAPK proteins, although phosphorylation alone is not sufficient for arachodonic acid release.

Whatever the mechanism of PLA₂ activation in any particular cell or context, the biological responses to PLA₂ inhibition observed in connection with this invention appear to be due to a decrease in spinal facilitation rather than an anti-inflammatory action at the periphery since no decrease in paw edema was observed with decreased hyperalgesia following intrathecal administration of a PLA₂ inhibitor. Furthermore, intraperitoneal administration of the same amount of PLA₂ inhibitor that was given intrathecally had no effect on the carrageenan-induced thermal hyperalgesia.

As demonstrated in Examples 6 and 7 and summarized in Table I, cPLA₂ and iPLA₂ activity in rat spinal cord can be decreased by PLA₂ inhibitors. Intrathecal administration of the cPLA₂ and iPLA₂ inhibitors methyl arachidonyl fluororphosphonate (MAFP) and arachidonyl trifluoromethylketone (AATFMK) dose dependently prevented thermal hyperalgesia induced by injection of carrageenan into the hind paw as well as formalin induced flinching, with no effect on normal motor function (see also, Examples 2 and 3): TABLE 1 Effect of Existing PLA₂ Inhibitors on Spontaneous Movement^(a) Agent Number of counts N Saline 367 ± 45 6 Vehicle 306 ± 36 6 AATFMK 298 ± 41 6 MAFP 311 ± 40 6 BEL_(b) 212 ± 32 6 ^(a)Spontaneous movement during 60 minutes after IT injection of saline, vehicle or PLA₂ inhibitors. Movement was quantified using the automated flinch counting device with the difference that no formalin was injected into the paw. Animals were acclimatized on the device and measurements started 10 minutes after IT administration of vehicle or drug. _(b)Intrathecal injection of the specific Group VI iPLA₂ inhibitor bromoenol lactone (BEL) reduced formalin induced flinching, but also suppressed spontaneous movement, possibly due to a sedation/motor dysfunction.

In contrast, although the COX enzymes are crucial to prostaglandin synthesis and their inhibition prior to injury has been shown to decrease hyperalgesia, IT administration of COX inhibitors after the onset of hyperalgesia cannot rescue hyperalgesic behavior (although partial mitigation of hyperalgesia is possible with IT AATFMK administered following the onset of inflammation). Thus, the inhibitory effect observed, coupled with the capacity of the inhibitors tested to clearly reduce PLA₂ activity in spinal homogenates (Examples 6 and 7), is strongly tied to modulation of PLA₂ activity.

C. Methods for Inhibition of PLA₂ in the CNS.

1. Activity of Existing PLA₂ Inhibitors.

As demonstrated above, known PLA₂ inhibitors (e.g., AATFMK and MAFP) have activity in the CNS. Other PLA₂ inhibitors are known to be active in a variety of mammalian cells (e.g., fatty acid tricarbonyl and trifluoromethyl ketones, as well as large-molecule pyrrolidine-based inhibitors), and so may also be active in spinal cord cells. However, many such inhibitors are neither reversible in their effect, nor are they entirely specific for PLA₂. Thus, while these inhibitors could inhibit spinally-mediated PLA₂ activity, better results will be obtainable with the specific and reversible PLA₂ inhibitors of the invention.

2. Novel 2-oxoamide PLA₂ Inhibitors: Activity and Structure.

A novel class of potent human PLA₂ inhibitors has been developed. These inhibitors contain the 2-oxoamide functionality and are described by Formula I:

-   -   wherein     -   R¹ is any acidic group, such as a carboxyl, phosphate,         phosphinate, sulfate, sulfonate, or tetrazolyl group; and,     -   R₂, R₃ is any aromatic, heterocyclic, or carbocyclic group or a         linear or branched, saturated or unsaturated alkyl, alkenyl, or         alkynyl chain;     -   n≧0, m≧0, k≧0.

Based on the inhibition activity studies whose data are summarized in Tables 2-5 below, preferred PLA₂ inhibitors are those which possess characteristics including, without limitation, one or more of the following:

-   -   (1) all are hydrophobic 2-oxoamides produced according to         general synthesis scheme (1) described in the following section         of this disclosure;     -   (2) the R₂ side chain substituents may be α-, β-, γ-, δ-, and         ε-amino acids;     -   (3) R₃ will possess more than 3 carbons, and preferably more         than 6, and most preferably greater than 10 carbons in length;     -   (4) the free carboxy moiety is preferably preserved (but         see, (8) below);     -   (5) the ether side chains will not be increased in length, if at         all, by more than about 11 carbons;     -   (6) inhibitors having distances between the carboxy moiety and         the oxoamide side chain comparable to the distance of the δ- or         γ-norleucines from the carboxy group in the norleucine compounds         are preferred, and the δ- and γ-norleucine variants are         particularly preferred;     -   (7) methylenes may be added to the R₃ side chain;     -   (8) polar substitutents may be substituted for the free carboxy         moiety of the inhibitors of the invention;     -   (9) for inhibition of cPLA₂ in particular, the molecule may be         negatively charged.

Among the compounds tested, a long-chain 2-oxoamide containing L-γ-norleucine was one of the most potent inhibitors, causing a 50% decrease in cPLA₂ activity at 0.009 mole fraction (compound “OA4”; see, Tables 2 and 3, as well as Examples 2 and 7). All of the data above are provided with respect to X_(I)(50), which is the mole fraction of inhibitor in the total substrate interface required to inhibit the enzyme by 50%. Almost all inhibitors of PLA₂'s partition into the phospholipid surface, because they usually have a hydrophobic nature that helps them bind to the active site of the PLA₂. When these inhibitors partition into the surface, an important physical effect called surface dilution comes into play. In this case, the strength of the interaction of PLA₂ and an inhibitor depends not on the bulk concentration of the inhibitor (molar units), but on the surface concentration of the inhibitor (mole fraction units).

The activity of several of the compounds synthesized and evaluated is summarized in the following Tables, and demonstrate that the compounds of the invention are potent PLA₂ inhibitors. As shown in FIGS. 12A and 12B, the inhibitory effect exhibited is fully reversible, making the inhibitory compounds of the invention particularly attractive candidates for use in therapeutic applications. TABLE 2 Identities, chemical structures, and inhibitory potencies of various 2-oxo-amide compounds towards iPLA₂, N.D. signifies that the X_(I)(50) values were not able to be determined because the compounds are poor inhibitors. N/A signifies that an X_(I)(50) value is given for the compound. Highest Conc. X_(I)(50) (mole fraction) Number Structure (mole fraction) w/ % Inhibition OA1

0.017 ± 0.009 N/A OA2

N.D. 0.091; 60% OA3

0.027 ± 0.004 N/A OA4

0.009 ± 0.004 N/A OA5

0.008 ± 0.003 N/A OA6

0.018 ± 0.009 N/A OA7

0.068 ± 0.005 N/A OA8

N.D. 0.02; 22% ± 7% OA9

0.035 ± 0.016 N/A OA10

0.045 ± 0.007 N/A OA11

0.047 ± 0.006 N/A OA12

0.017 ± 0.006 N/A OA13

0.033 ± 0.013 N/A OA14

0.021 ± 0.006 N/A OA15

0.044 ± 0.007 N/A OA16

N.D. 0.091, 60% OA17

N.D. 0.091; 24% OA18

N.D. 0.091; 24%

TABLE 3 Identities, chemical structures, and inhibitory potencies of various 2-oxo-amide compounds towards iPLA₂. N.D. signifies that the X_(I)(50) values were not able to be determined because the compounds are poor inhibitors or the stock concentrations do not permit a full dose dependent analysis. N/A signifies that an X_(I)(50) value is given for the compound. Highest Conc. X_(I)(50) (mole fraction) Number Structure (mole fraction) w/ % inhibition OA19

0.0158 ± .0009 N/A OA20

N.D. 0.091: 55% ± 4% OA21

N.D. 0.020: 38% ± 6% OA22

N.D. 0.020: 31% ± 6% OA23

N.D. 0.020: 43% ± 4% OA24

N.D. 0.020: 60% ± 6%

TABLE 4 Indentities, chemical structures and inhibitory potencies of various 2-oxo-amide compounds towards both iPLA₂ and cPLA₂. N.D. signifies that the X_(I)(50) values were not able to be determined because the compounds are poor inhibitors. N/A signifies that an X_(I)(50) value is given for the compound. Highest Conc. X_(I)(50) (mole fraction Number Structure (mole fraction) w/ % Inhibition OA25

C PLA₂: N.D. I PLA₂: 0.0142 ± 0.0004 cPLA₂: 0.091: 41% iPLA₂: N/A OA26

cPLA₂: 0.028 ± 0.017 iPLA₂: 0.018 ± 0.002 cPLA₂: N/A iPLA₂: N/A

TABLE 5 Indentities and chemical structures of 2-oxo-amide compounds which show no inhibition of either cPLA₂ or iPLA₂. Number Structure OA27

OA28

OA29

OA30

OA31

OA32

OA33

OA34

OA35

OA36

OA37

OA38

These data demonstrate both the necessary and desirable characteristics of the PLA₂ inhibitors of the invention. For example, the length of the R₃ substituent is significant. Using leucine and phenylalanine variants, the role of the saturated chain length (R₃ position, see Formula I) off the 2-oxo acid moiety (13 carbons) was explored. When the length was shortened to 6 carbons or 10 carbons the potency went down about 4-fold and 2-fold respectively. OA29, a γ-carbamate with a shorter R₃ substituent, did not inhibit cPLA₂ (Table 5), while a longer chain at the R₃ position produces a moderate level of inhibition (OA15, Table 2). This same effect is seen in comparison of the activities of OA28 and OA1 (in Table 5 and Table 2, respectively).

While the invention is not intended to be limited by its mechanism of action, it is possible that partitioning to the lipid micelles is affected by less hydrophobic shortened acyl chains or, more likely, results from a weaker interaction with the deep hydrophobic active site of cPLA₂. This is suggested by the lack of inhibition of cPLA₂ by compounds with an R₃ phenyl substituent linked to the 2-oxoamide by 4- or 3-methylene groups (OA35 and OA36, Table 5). These compounds have a shorter substituent that is also bulkier, which might also affect their activity. As expected, the carboxymethyl ester versions of these two compounds also do not inhibit cPLA₂ (OA20 and OA34, Table 3 and Table 5, respectively).

Further, activity appears to depend in part on the presence of the free carboxy group (see Table 2 and compare data for OA1 and OA8). Inhibitory potency can alternatively be enhanced to a degree by addition of relatively polar substituents to the molecule. This phenomenon is demonstrated by OA25 (Table 5), which has a lactone in place of the carboxy and γ-side chain, and is therefore uncharged. As would be expected, OA25 is a fairly poor inhibitor of cPLA₂, but does possess some inhibitory activity at 0.091 mole fraction. In contrast, OA19, the carboxymethyl ester (Table 3), exhibits no inhibitory activity. Further illustration of this phenomenon is provided by OA26 (Table 5), which is a carboxymethyl ester variant of the free carboxy-containing carbamate OA30 (Table 5). OA30 does not inhibit cPLA₂, while OA26 does, notwithstanding the absence therein of a free carboxy moiety. OA26's activity is most likely due to incompatibility between the polarities of the carbamate side chain and the free carboxy group with the cPLA₂ active site, while the polarity of the carbamate and carboxymethyl ester are better suited.

Therefore, taking into account the composition of the cPLA₂ active site, it is possible to substitute polar substitutents for the free carboxy moiety of the inhibitors of the invention, while retaining a degree of inhibitory activity. As such, these polar substituted molecules are within the scope of the invention. Nonetheless, inhibitor molecules having the free carboxy moiety are generally preferred.

Activity in cPLA₂ inhibitors is also enhanced by the existence of a negative charge in the inhibitor, as indicated by the lack of inhibition provided by a variant of OA1 that contained a carboxymethyl ester in place of the free carboxy (OA19, Table 3). OA19 has no measurable inhibition against cPLA₂ at up to 0.091 mole fraction.

Potency is also enhanced by an increase in relative distance between the oxoamide group and the carboxy group (see, Table 2, comparison of activity in α-, β-, γ-, δ-, and ε-amino acid variants of OA4 (OA2, OA3, OA4, OA5, and OA6, respectively). In particular, as the carboxy moiety is moved further away from the norleucine side chain, the inhibitory potency increases. For example, α-amino acid variant, OA2, is a relatively poor inhibitor (around 7-fold less potent than OA4). The β-norleucine displays better inhibitory activity; i.e., around 3-fold less potency than OA4. The δ-norleucine has inhibitory activity essentially equivalent to that of OA4. However, consistent with the leveling off of inhibitory potency from the δ- to γ-norleucines, the ε-amino acid variant, OA6, was around 2-fold less potent than OA4 (Table 2). As such, inhibitors having distances between the carboxy moiety and the oxoamide moiety comparable to the distance of the δ- or γ-norleucines from the carboxy group are preferred, and the δ- and γ-norleucine variants are particularly preferred.

In addition to use of the δ- or γ-norleucine variants, distance and hydrophobicity may be provided in the inhibitors of the invention by other modifications, which those of ordinary skill in the art may identify, such as the addition of one or more methylenes to increase hydrophobicity. For example, the R₃ substituent (see Formula I), varies from 9 methylenes in OA2, OA4 and OA6, to 12 methylenes in OA3 and OA5. As a longer R₃ substituent appears to benefit the inhibitory potency, a γ-norleucine with 12 methylenes at the R₃ position can be reasonably expected to be more potent that the 9 methylene γ-norleucine (OA4) or even the 12 methylene δ-norleucine (OA5).

However, the data also indicate a limitation on variation in the inhibitory compounds' structures. A significant overall increased length of the ether side chains may not be tolerated by the cPLA₂ active site in particular. While the L-γ-norleucine 2-oxoamide (OA4) is quite potent against cPLA₂ activity, substitution of a longer (11 carbon) ether containing side chain in place of the norleucine side chain results in a 5-fold decrease in inhibitory potency by both stereoisomers (FIG. 13). The linear (vs logarithmic) shape of the data indicates a poor inhibition which is confirmed by the X_(I)(50) for both enantiomers at around 0.045 mole fraction, suggesting that the cPLA₂ active site may have some intolerance for the more polar heteroatoms at this position. This hypothesis is farther supported by the lack of inhibition by side chains containing a carbamate (e.g., OA16, OA30 and OA32, Tables 2 and 4) or amide (e.g., OA31 and OA29, Table 4), which had essentially no measurable inhibition of cPLA₂.

3. Synthesis of Novel 2-oxoamide PLA₂ Inhibitors.

General structures and synthesis schemes for the compounds described in the foregoing Tables, and others, are provided below. Synthesis of a number of representative simple primary and secondary 2-oxoamides, as well as four derivatives containing a free carboxyl group, is shown. Synthesis of a specific, representative inhibitory compound, OA4, is also detailed in Example 8.

Synthesis of the inhibitors of the invention can be achieved beginning with the first and second steps outlined above in Scheme 1, and as repeated below in Scheme 2. In both schemes, N-protected amino alcohols 1 are prepared from the corresponding natural or unnatural α-amino acids by the mixed anhydride-NaBH₄ or the acyl fluoride-NaBH₄ method. Alcohols 1 are oxidized to the corresponding aldehydes by NaOCl in the presence of a catalytic amount of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-yloxy free radical (AcNH-TEMPO) and the aldehydes 2 are directly used in the next step without any purification.

In Scheme 1, step (i) generally represents alternative Steps 3, 4 and/or 5, and equivalents, as depicted in Scheme 2. Step (ii) generally represents Steps 6, 7 and/or 8, and equivalents, as depicted in Scheme 2. Step (iii) generally represents Step 9, and equivalents, as depicted in Scheme 2, while step (iv) is collectively representative of the steps for alternative routes of synthesis depicted in Schemes 3-9.

There are three routes for the synthesis of γ-amino acid based 2-oxoamide inhibitors depending on the ylide and the N-protecting group used (Scheme 2). Wittig reaction of Boc-protected amino aldehydes 2 with benzyl or methyl (triphenylphosphoranylide)acetate leads to α,β-unsaturated esters 3 and 4. The Boc group is removed, and the amino component is coupled with 2-hydroxy acids using 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide (WSCI) in the presence of hydroxybenzotriazole (HOBt). Catalytic hydrogenation of 6 and 7, combined with saponification in the case of 7, followed by oxidation with either PDC or NaOCl/AcNH-TEMPO leads to the target compounds 9. Z-Protected amino aldehydes 2 are treated with tert-butyl triphenylphosphoranylidene)acetate to give compound 5. After catalytic hydrogenation the amino component is coupled with 2-hydroxy acids by the WSCI/HOBt method. Oxidation of 8 followed by removal of tert-butyl group with CF₃COOH leads to compounds 9.

Reagents and conditions: (a) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.; (b) Ph₃P═CHCO₂Y, THF, reflux; (c) 4N HCl/Et₂O; (d) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (e) H₂, 10% Pd/C; (f) 1N NaOH, dioxane/H₂O 9:1; (g) 50% CF₃CO₂H/CH₂Cl₂.

For the synthesis of ε-amino acid based inhibitors, alcohols 1 are converted into aldehydes and reacted with triethyl phosphonocrotonate (Scheme 3). Catalytic hydrogenation of compounds 10, removal of the protecting group and coupling with 2-hydroxy acids gives compounds 11. Saponification, followed by oxidation, leads to compounds 12.

Reagents and conditions: (a) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.; (b) (EtO)₂P(═O)CH₂CH═CHCO₂Et, LiOH, THF; (c) H₂ 10% Pd/C; (d) 4N HCl/Et₂O; (e) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (f) 1N NaOH, dioxane/H₂O 9:1.

For the synthesis of α-amino acid based inhibitors, methyl esters of α-amino acids 13 are coupled with 2-hydroxy acids (Scheme 4). Saponification of 14, followed by oxidation, leading to compounds 15.

Reagents and conditions: (a) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (b) 1N NaOH, dioxane/H₂O 9:1; (c) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.

Likewise, β-amino acid based 2-oxoamide inhibitors can be prepared from β-amino acid esters following the route depicted in Scheme 4 for α-amino acid based inhibitors. Alternatively, for the synthesis of β-amino acid based inhibitors, N-(tert-butoxycarbonyl)-phenylalaninol 16 may be used as a starting material. Compound 16 is oxidized and treated with alkylidene phosphoranes to produce compounds 17 (Scheme 5). Removal of the protecting group and coupling with 2-hydroxy acids leads to compounds 18, which are hydrogenated. The phenyl group is converted to carboxylic acid by oxidation with NaIO₄, RuCl₃ in MeCN, EtOAc, H₂O (1:1:8).

Reagents and conditions: (a) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.; (b) CH₃(CH₂)_(n)CH₂P⁺Ph₃Br⁻, KHMDS, toluene, −78° C.; (c) H₂ 10% Pd/C; (d) 4N HCl/Et₂O; (e) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (f) NaIO₄, RuCl₃, MeCN/EtOAc/H₂O 1:1:8.

For the synthesis of δ-amino acid based inhibitors, Boc-protected amino alcohols 1 were oxidized and reacted with the ylide generated from Br⁻Ph₃P⁺CH₂CH₂C₆H₅ (Scheme 6). Removal of the protecting group of 20 and coupling with 2-hydroxy acids led to compounds 21. After catalytic hydrogenation, oxidative conversion of the phenyl group to carboxylic acid led to compounds 22.

Reagents and conditions: (a) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.; (b) PhCH₂CH₂P⁺Ph₃Br⁻, KHMDS, toluene, −78° C.; (c) 4N HCl/Et₂O; (d) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (e) H₂ 10% Pd/C; (f) NaIO₄, RuCl₃, MeCN/EtOAc/H₂O 1:1:8.

The synthesis of inhibitors based on homologated amino acids may also be accomplished as depicted in Scheme 7. Boc-Protected amino aldehydes, produced from 1, are reacted with the ylides generated from I-Ph₃P⁺CH₂(CH₂)_(n)OTr. Removal of the protecting group of 23 and coupling with 2-hydroxy acids leads to compounds 24. Catalytic hydrogenation and oxidation by NaOCl/AcNH-TEMPO in the presence of a phase-transfer catalyst leads to compounds 25.

Reagents and conditions: (a) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.; (b) TrO(CH₂)_(n)CH₂P⁺Ph₃I⁻, KHMDS, toluene, −78° C.; (c) 4N HCl/Et₂O; (d) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (e) H₂ 10% Pd/C; (f) NaOCl, AcNH-TEMPO, Bu₄N⁺HSO₄ ⁻, NaBr, NaHCO₃, CH₂Cl₂/H₂O, 0° C.

Glutamic acid based 2-oxoamides can be prepared as depicted in Schemes 8 and 9. γ-Methyl tert-butoxycarbonyl-glutamate 26 was coupled with amines by the WSCI/HOBt method. Removal of the protecting group and coupling with 2-hydroxy acids led to compounds 28. Compounds 29 were produced by saponification of 28 and oxidation with NaOCl/AcNH-TEMPO. Alcohol 30 was converted into carbamates 31 by treatment with alkyl isocyanates. Removal of the protecting group and coupling with 2-hydroxy acids led to compounds 32. Compounds 33 were produced by saponification of 32 and oxidation with NaOCl/AcNH-TEMPO.

Reagents and conditions: (a) CH₃(CH₂)_(n)NH₂, WSCI, HOBt; (b) 4N HCl/MeOH; (c) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (d) 1N NaOH/MeOH; (e) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, 5° C.

Reagents and conditions: (a) CH₃(CH₂)_(n)NCO, DMAP; (b) 4N HCl/MeOH; (c) R²(CH₂)_(m)CHOHCO₂H, WSCI, HOBt; (d) 1N NaOH/MeOH; (e) NaOCl, AcNH-TEMPO, NaBr, NaHCO₃, toluene/EtOAc/H₂O 3:3:0.5, −5° C.

Analytical Data for Particular Inhibitory Compounds

(4R)-5-(Decyloxy)-4-[(2-oxododecanoyl)amino]pentanoic Acid (OA11)

[α]D−16.2 (c 0.5 CHCl₃). 1H NMR: δ 7.24 (1H, d, CONH, J=9.4 Hz), 4.08 (1H, m, CHNH), 3.42 (4H, m, 2×CH₂O), 2.90 (2H, t, CH₂COCO, J=7.8 Hz) 2.39 (2H, t, CH₂COOH, J=7.0 Hz), 1.99 (2H, m, CH₂CH₂COOH), 1.58 (4H, m, CH₂CH₂COCO, CH₂CH₂O), 1.26 (28H, m, 14×CH₂), 0.88 (3H, t, J=6.0 Hz, CH₃). 13C NMR: δ 199.0, 178.4, 160.0, 71.6, 69.7, 48.7, 36.8, 31.8, 29.6, 29.4, 29.3, 29.0, 26.0, 23.1, 22.6, 14.1.

(3S)-(2-Oxo-pentadecanoylamino)-heptanoic Acid (OA3)

1H NMR: δ 7.31 (1H, d, J=9 Hz, NH), 4.20 (1H, m, CH), 2.91 (2H, t, J=7.8 Hz, CH₂COCO), 2.61 (2H, d, J=5 Hz, CH₂COOH), 1.60 (4H, m, 2×CH₂), 1.25 (24H, m, 12×CH₂), 0.88 (6H, t, J=6.8 Hz, 2×CH₃). 13C-NMR: δ 199.2, 176.4, 159.7, 46.1, 38.2, 36.8, 33.5, 31.9, 29.6, 29.4, 29.3, 29.0, 28.1, 23.1, 22.7, 22.3, 14.1, 13.9.

(5S)-5-(2-Oxopentadecanoylamino)-nonanoic Acid (OA5)

1H NMR: δ 6.73 (1H, d, J=9 Hz, NH), 3.87 (1H, m, CH), 2.92 (2H, t, J=7.8 Hz, CH₂COCO), 2.35 (2H, m, CH₂COOH), 1.72-1.46 (8H, m, 4×CH₂), 1.25 (24H, m, 12×CH₂), 0.88 (6H, t, J=6.8 Hz, 2×CH₃).

13C-NMR: δ 199.6, 178.3, 159.9, 49.3, 36.8, 34.6, 34.2, 33.4, 31.9, 29.6, 29.4, 29.3, 29.0, 27.9, 23.2, 22.7, 22.5, 20.9, 14.1, 13.9.

(4S)-4-(2-Oxopentadecanoylamino)-heptanoic Acid (OA14)

1H NMR: δ 6.93 (1H, d, J=9 Hz, NH), 4.03 (1H, m, CH), 2.91 (2H, t, J=7.8 Hz, CH₂COCO), 2.39 (2H, m, CH₂COOH), 1.85 (2H, m, CH₂), 1.59 (2H, m, CH₂), 1.25 (23H, m, 10×CH₂, CH₃), 0.88 (3H, t, J=6.7 Hz, CH₃). 13C-NMR: δ 199.4, 178.3, 159.7, 45.1, 36.7, 31.9, 31.3, 30.7, 29.6, 29.4, 29.3, 29.0, 23.1, 22.7, 20.7, 14.1.

(4R)-6-Methyl-4-(2-oxo-dodecanoylamino)-heptanoic Acid (OA13)

1H NMR: δ 6.83 (1H, d, J=9 Hz, N, 4.02 (1H, m, CH), 2.91 (2H, t, J=7.8 Hz, CH₂COCO), 2.36 (2H, m, CH₂COOH), 1.91 [3H, m, CH₂, CH(CH₃)₂], 1.59 (4H, m, 2×CH₂), 1.25 (14H, m, 7×CH₂), 0.91 (9H, t, J=6.8 Hz, 3×CH₃). 13C-NMR: δ 199.4, 178.4, 160.1, 47.4, 44.3, 36.8, 31.8, 30.7, 30.4, 29.5, 29.4, 29.3, 29.2, 29.0, 24.9, 23.2, 22.9, 22.6, 22.0, 14.1.

(6S)-6-(2-Oxo-dodecanoylamino)-decanoic Acid (OA6)

1H NMR: δ 6.72 (1H, d, J=9 Hz, NH), 3.85 (1H, m, CH), 2.90 (2H, t, J=7.8 Hz, CH₂COCO), 2.31 (2H, t, J=7.4 Hz, CH₂COOH), 1.78-1.23 (28H, m, 14×CH₂), 0.88 (6H, t, J=6.8 Hz, 2×CH₃). 13C-NMR: δ 199.7, 179.3, 159.8, 49.4, 36.8, 34.6, 33.7, 31.8, 29.5, 29.4, 29.3, 29.0, 27.9, 25.3, 24.4, 23.2, 22.6, 22.5, 14.1, 13.9.

(4R)-4-(2-Oxo-pentadecanoylamino)-5-phenyl-pentanoic Acid (OA9)

1H NMR: δ 7.33-7.14 (5H, m, C₆H₅), 6.97 (1H, d, J=9 Hz, NH), 4.20 (1H, m, CH), 2.86 (4H, m, CH₂C₆H₅, CH₂COCO), 2.37 (2H, t, J=7.2 Hz, CH₂COOH), 1.95 (1H, m, CHH), 1.81 (1H, m, CHH), 1.56 (2H, m, CH₂), 1.26 (20H, m, 10×CH₂), 0.89 (3H, t, J=6.8 Hz, CH₃). 13C-NMR: δ199.2, 178.0, 160.0, 136.9, 129.2, 128.6, 126.8, 50.3, 41.1, 36.7, 31.9, 30.7, 29.6, 29.4, 29.3, 29.0, 28.9, 23.1, 22.7, 14.1.

(2S)-2-(2-Oxo-pentadecanoylamino)-hexanoic Acid (OA2)

1H NMR: δ7.41 (1H, d, J=9 Hz, NH), 4.52 (1H, m, CH), 2.90 (2H, t, J=7.8 Hz, CH₂COCO), 2.00-1.56 (6H, m, 3×CH₂), 1.25 (16H, m, 8×CH₂), 0.88 (6H, 1, J=6.7 Hz, 2×CH₃). 13C-NMR: δ 198.5, 176.4, 159.9, 52.8, 36.8, 31.9, 29.6, 29.4, 29.3, 29.0, 27.4, 23.1, 22.7, 22.3, 14.1, 13.8.

(4R)-4-(2-Oxo-octanoylamino)-5-phenyl-pentanoic Acid (OA17)

1H NMR: δ7.38-7.14 (5H, m, C₆H₅), 6.95 (1H, d, J=9 Hz, NH), 4.20 (1H, m, CH), 2.86 (4H, m, CH₂C₆H₅, CH₂COCO), 2.37 (2H, t, J=7.4 Hz, CH₂COOH), 1.97 (1H, m, CHH), 1.78 (1H, m, CHH), 1.57 (2H, m, CH₂), 1.26 (6H, m, 3×CH₂), 0.87 (3H, t, J=6.8 Hz, CH₃). 13C-NMR: δ199.2, 177.6, 160.0, 136.9, 128.7, 128.1, 127.0, 50.3, 41.1, 36.7, 31.5, 28.7, 26.3, 22.4, 14.0.

(4R)-6-Methyl-4-(2-oxo-pentadecanoylamino)-heptanoic Acid (OA12)

1H NMR: δ 6.95 (1H, d, J=9.2 Hz, NH), 4.00 (1H, m, CH), 2.91 (2H, t, J=7.8 Hz, CH₂COCO), 2.30 (2H, m, CH₂COOH), 1.91 [3H, m, CH₂, CH(CH₃)₂], 1.59 (4H, m, 2×CH₂), 1.25 (20H, m, 10×CH₂), 0.91 (9H, t, J=6.8 Hz, 3×CH₃). 13C-NMR: δ 199.3, 178.8, 160.0, 47.3, 44.1, 36.8, 31.8, 31.1, 30.4, 29.5, 29.3, 29.2, 28.9, 24.7, 23.0, 22.9, 22.5, 21.9, 22.5, 13.9.

3-[1-(2-Oxo-pentadecanoyl)-pyrrolidin-2-yl]propionic Acid (OA18)

1H NMR: δ4.21 (1H, m, CH), 3.54 (2H, m, CH₂NH), 2.84 (2H, m, CH₂COCO), 2.35 (2H, m, CH₂COOH), 2.01-1.41 (8H, m, 4×CH₂), 1.25 (20H, m, 10×CH₂), 0.86 (3H, t, J=6.6 Hz, CH₃). 13C-NMR: δ 201.0, 177.9, 163.6, 57.1, 47.2, 39.2, 31.8, 31.1, 30.2, 29.6, 29.4, 29.3, 29.1, 29.0, 28.4, 24.2, 22.9, 22.6, 21.1, 14.1.

3-[1-(2-Oxo-dodecanoyl)-pyrrolidin-2-yl]propionic Acid (OA37)

1H NMR: δ 4.21 (1H, m, CH), 3.54 (2H, m, CH₂NH), 2.84 (2H, m, CH₂COCO), 2.35 (2H, m, CH₂COOH), 2.01-1.41 (8H, m, 4×CH₂), 1.25 (14H, m, 7×CH₂), 0.86 (3H, t, J=7 Hz, CH₃). 13C-NMR: δ201.0, 177.6, 164.1, 57.1, 47.2, 39.3, 31.9, 31.2, 29.5, 29.4, 29.3, 29.1, 28.6, 24.2, 22.9, 22.6, 14.1.

5-octylcarbamoyloxy-4-(S)-(2-oxo-dodecanoylamino)-pentanoic Acid (OA16)

[α]_(D)−16.8.8 (c 0.26 CHCl₃). 1H NMR: δ7.22 (1H, m, NHCO), 4.85 (1H, m, OCONH), 4.15 (3H, m, CH, CH₂OCONH), 3.15 (2H, m, NHCH₂), 2.91 (2H, t, J=7.8 Hz, COCOCH₂), 2.40 (2H, m, CH₂COOH), 1.90 (2H, m, CH₂), 1,70-1,40 (4H, m, 2×CH₂), 1.27 (24H, m, 12×CH₂), 0.89 (6H, t, J=6.8 Hz, 2×CH₃). 13C NMR: δ 198.9, 176.9, 160.2, 156.0, 65.5, 48.6, 41.2, 36.8, 31.9, 31.8, 30.3, 29.8, 29.5, 29.4, 29.3, 29.2, 29.0, 26.7, 26.3, 23.1, 22.6, 14.1.

5-ethylcarbamoyloxy-4-(S)-(2-oxo-dodecanoylamino)-pentanoic Acid (OA30)

[α]_(D)−25.6 (c 1 CHCl₃). m.p. 70-720 C. 1H NMR: δ 7.25 (1H, m, NHCOCO), 4.85 (1H, m, OCONH, 4.15 (3H, m, CH₂OCONH, CH), 3.20 (2H, m, NHCH₂), 2.90 (2H, t, J=7.4 Hz, CH₂COCO), 2.42 (2H, m, CH₂COOH), 1.93 (2H, m, CH₂), 1.59 (2H, m, CH₂), 1.29 (14H, m, 7×CH₂), 1.14 (3H, t, J=7.4 Hz, NHCH₂CH₃), 0.88 (3H, t, J=7 Hz, CH₃). 13C NMR: δ 198.8, 177.3, 160.1, 156.0, 65.5, 48.4, 36.7, 35.9, 31.8, 30.3, 29.4, 29.3, 29.2, 29.0, 28.9, 26.2, 23.0, 22.6, 15.0, 14.1.

5-ethylcarbamoyloxy-4-(R)-(2-oxo-dodecanoylamino)-pentanoic Acid (OA32)

[α]_(D)+26.1 (c 1 CHCl₃).m.p. 70-720 C. 1H NMR: δ7.25 (1H, m, NHCOCO), 4.82 (1H, m, OCONH), 4.19 (3H, m, CH₂OCONH, CH), 3.21 (2H, m, NHCH₂), 2.90 (2H, t, J=7.4 Hz, CH₂COCO), 2.42 (2H, m, CH₂COOH), 1.98 (2H, m, CH₂), 1.59 (2H, m, CH₂), 1.29 (14H, m, 7×CH₂), 1.14 (3H, t, J=7.4 Hz, NHCH₂CH₃), 0.88 (3H, t, J=7.0 Hz, CH₃). 13C NMR: δ 198.7, 177.0, 160.0, 155.9, 65.4, 48.4, 36.6, 35.8, 31.7, 30.2, 29.4, 29.2, 29.1, 28.9, 26.1, 22.9, 22.5, 15.0, 13.9.

4-Ethylcarbamoyl-4-(S)-(2-oxo-dodecanoylamino)-butyric Acid (OA29)

1H NMR: δ 8.10 (1H, d, J=9 Hz, NHCOCO), 7.20 (1H, m, CON), 4.65 (1H, m, CH), 3.30 (2H, m, NHCH₂), 2.87 (2H, t, J=7.4 Hz, CH₂COCO), 2.45 (2H, m, CH₂COOH), 2.11 (2H, m, CH₂), 1.57 (2H, m, CH₂), 1.25 (14H, m, 7×CH₂), 1.15 (3H, t, J=7.0 Hz, NHCH₂CH₃), 0.87 (3H, t, J=6.6 Hz, CH₃). 13C NMR: δ 198.0, 176.2, 170.6, 160.5, 52.1, 37.0, 34.7, 31.8, 29.8, 29.5, 29.4, 29.3, 29.2, 29.0, 27.5, 23.0, 22.6, 14.4, 14.1.

4-Ethylcarbamoyl-4-(R)-(2-oxo-dodecanoylamino)-butyric Acid (OA31)

[α]_(D)+11.6 (c 0.5 CHCl₃).m.p. 109-1120 C. 1H NMR: δ 8.02 (1H, d, J=9 Hz, NHCOCO), 7.03 (1H, m, CONH), 4.63 (1H, m, CH), 3.32 (2H, m, NHCH₂), 2.89 (2H, t, J=7.4 Hz, CH₂COCO), 2.49 (2H, m, CH₂COOH), 2.12 (2H, m, CH₂), 1.59 (2H, m, CH₂), 1.23 (14H, m, 7×CH₂), 1.17 (3H, t, J=7.0 Hz, NHCH₂CH₃), 0.88 (3H, t, J=6.6 Hz, CH₃). 13C NMR: δ 197.9, 175.9, 170.1, 160.2, 52.0, 36.8, 34.5, 31.7, 29.7, 29.4, 29.3, 29.2, 29.1, 28.9, 27.6, 22.9, 22.5, 14.3, 14.0.

4-Decylcarbamoyl-4-(S)-(2-oxo-hexadecanoylamino)-butyric Acid (OA15)

[α]_(D)−10.2 (c 0.5 CHCl₃). m.p. 91-930 C. 1H NMR: δ7.95 (1H, d, J=9.2 Hz, NHCOCO), 6.99 (1H, m, CONH), 4.66 (1H, m, CH), 3.25 (2H, m, NHCH₂), 2.87 (2H, t, J=7.2 Hz, CH₂COCO), 2.46 (2H, m, CH₂COOH), 2.10 (2H, m, CH₂), 1.54 (4H, m, 2×CH₂), 1.23 (36H, m, 18×CH₂), 0.88 (6H, t, J=6.6 Hz, 2×CH₃). 13C NMR: δ 197.8, 175.9, 170.2, 160.3, 52.1, 39.8, 37.1, 31.9, 29.6, 29.5, 29.4, 29.3, 29.0, 27.7, 26.8, 23.0, 22.7, 14.1.

2-(S)-(2-Oxo-dodecanoylamino)-pentanedioic Acid (OA33)

[α]_(D)+24.4 (c 0.5 CHCl₃). m.p. 97-98° C. 1H NMR: δ 7.61 (1H, d, J=9.2 Hz, NHCOCO), 4.61 (1H, m, CH), 2.91 (2H, t, J=7.4 Hz, CH₂COCO), 2.54 (2H, m, CH₂COOH), 2.31 (2H, m, CH₂), 1.61 (2H, m, CH₂), 1.26 (14H, m, 7×CH₂), 0.88 (3H, t, J=6.6 Hz, CH₃). 13C NMR: δ 198.1, 178.7, 176.5, 159.8, 51.2, 36.7, 31.9, 29.5, 29.4, 29.3, 29.0, 26.1, 23.1, 22.7, 14.1.

4-(2-Oxo-6-phenyl-hexanoylamino)-butyric Acid (OA35)

m.p. 60-620 C. 1H NMR: δ7.27-7.15 (6H, m, C₆H₅, NHCOCO), 3.35 (2H, m, CH₂NH), 2.94 (2H, t, J=7.4 Hz, CH₂COCO), 2.60 (2H, m, CH₂), 2.38 (2H, m, CH₂), 1.86 (2H, m, CH₂), 1.64 (4H, m, 2×CH₂). 13C NMR: δ 198.8, 178.8, 160.3, 142.0, 128.3, 125.7, 38.6, 36.5, 31.4, 30.7, 24.2, 22.6.

4-(2-Oxo-5-phenyl-pentanoylamino)-butyric Acid (OA36)

m.p. 65-670 C. 1H NMR: δ7.25-7.11 (6H, m, C₆H₅, NHCOCO), 3.33 (2H, m, CH₂NH), 2.86 (2H, t, J=7.4 Hz, CH₂COCO), 2.60 (2H, m, CH₂), 2.36 (2H, m, CH₂), 1.86 (2H, m, CH₂), 1.64 (4H, m, 2×CH₂). 13C NMR: δ 198.8, 178.5, 160.3, 141.2, 128.4, 126.0, 38.5, 36.1, 34.9, 31.2, 24.7, 24.0.

4-[(2-oxooctanoyl)amino]butanoic Acid (OA28)

¹H NMR δ 7.22 (1H, m, NM, 3.38 (2H, m, CH₂NH), 2.91 (2H, t, J=7 Hz, CH₂CO), 2.39 (2H, t, J=7 Hz, CH₂COOH), 1.88 (2H, m, CH₂CH₂COOH), 1.58 (2H, m, CH₂CH₂CO), 1.25 (6H, m, 3 CH₂), 0.83 (3H, t, J=7 Hz, CH₃); ¹³C NMR δ 199.2, 178.4, 160.4, 38.5, 36.7, 31.5, 31.2, 28.6, 24.1, 22.4, 13.9

4-[(2-oxohexadecanoyl)amino]butanoic acid (OA1). ¹H NMR δ 7.20 (1H, m, NH), 3.36 (2H, m, CH₂NH), 2.90 (2H, t, J=7 Hz, CH₂CO), 2.39 (2H, t, J=7 Hz, CH₂COOH), 1.87 (2H, m, CH₂CH₂COOH), 1.56 (2H, m, CH₂CH₂CO), 1.25 (22H, m, 11 CH₂), 0.83 (3H, t, J=7 Hz, CH₃); ¹³C NMR δ 199.2, 178.3, 160.4, 38.5, 36.4, 31.9, 30.9, 29.6, 29.3, 29.0, 24.2, 22.6, 14.1.

(4S)-4-[(2-Oxododecanoyl)amino]octanoic acid. (OA4) mp 50-52° C.; [α]_(D)−1.8 (c 0.5 CHCl₃); MS (FAB): m/z (%): 378 (35) [m+Na⁺], 356 (45) [m+H⁺]; ¹H NMR δ 6.86 (1H, d, J=9.4 Hz, NH), 3.90 (1H, m, CHNH), 2.90 (2H, t, J=7.8 Hz, CH₂COCO), 2.35 (2H, t, J=6.3 Hz, CH₂COOH), 2.01-1.05 (24H, m, 12CH₂), 0.87 (3H, t, J=6.0 Hz, CH₃); ¹³C NMR δ 199.4, 178.5, 160.1, 49.3, 36.8, 34.7, 31.8, 30.7, 29.8, 29.5, 29.4, 29.3, 29.2, 29.0, 27.9, 23.1, 22.6, 22.4, 14.1, 13.9.

(4R)-4-[(2-Oxododecanoyl)amino]octanoic acid (“OA7”). Spectroscopic data was identical to those obtained for the (S)-enantiomer.

D. Pharmaceutical PLA₂ Inhibitory Compositions and Use Thereof.

For use in therapeutic applications (e.g., treatment for pain, inflammation, or hyperalgesia), the particular amount of PLA₂ inhibitor to be delivered will depend on many factors, including the effect to be achieved, the type of organism to which the composition is delivered, delivery route, dosage regimen, and the age, health, and sex of the organism. As such, the particular dosage is left to the ordinarily skilled artisan's discretion.

The formulation of therapeutic compositions and their subsequent administration is believed to be within the skill of those in the art. Dosing is dependent on severity and responsiveness of the disease state to be treated, with the course of treatment lasting from several days to several months, or until a cure is effected or a diminution of the disease state is achieved. Optimal dosing schedules can be calculated from measurements of drug accumulation in the body of the patient. Persons of ordinary skill can easily determine optimum dosages, dosing methodologies and repetition rates. Optimum dosages may vary depending on the relative potency of individual inhibitors, and can generally be estimated based on X_(I)(50) found to be usually effective in in vitro and in vivo animal models (see, e.g., Example 7). In general, dosage is from 0.01 μg to 100 g per kg of body weight, and may be given once or more daily, weekly, monthly or yearly, as needed.

Toxicity is expected to be low or absent at clinically effective dosages of PLA₂ inhibitors of the invention. The data provided in the examples were obtained with no evidence of cytotoxicity in the ex vivo treated cells, or in animals treated in vivo. Further, gene-targeted mice who lack Group IVA PLA₂ altogether are much less prone to inflammatory pathological responses to disease, stresses, and physical injuries, which in essence protects them from cellular and systemic damage. These animals are fairly normal in all other respects suggesting that substantial inhibition of cPLA₂ activity should not have deleterious effects, especially over the course of relatively short-term treatments. Indeed, use of the PLA₂ inhibitors and methods of the invention to treat various inflammatory conditions should avoid many side effects and drawbacks of current therapies and treatments.

The PLA₂ inhibitors of the invention may be administered in any form including pharmaceutically acceptable salts, esters, or salts of such esters, or any other compound which, upon administration to an animal including a human, is capable of providing (directly or indirectly) the biologically active metabolite or residue thereof. The term “pharmaceutically acceptable salts” refers to physiologically and pharmaceutically acceptable salts of the compounds of the invention: i.e., salts that retain the desired biological activity of the parent compound and do not impart undesired toxicological effects thereto.

In addition, the invention encompasses administration of prodrug forms of PLA₂ inhibitors; i.e., those prepared in an inactive form that is converted to an active form (drug) within the body or cells thereof by the action of endogenous enzymes or other chemicals and/or conditions. Accordingly, the invention encompasses prodrugs and pharmaceutically acceptable salts of the PLA₂ inhibitors of the invention.

Pharmaceutically acceptable base addition salts are formed with metals or amines, such as alkali and alkaline earth metals or organic amines. Examples of metals used as cations are sodium, potassium, magnesium, calcium, and the like. Examples of pharmaceutically useful amines are N,N′-dibenzylethylenediamine, chloroprocaine, choline, diethanolamine, dicyclohexylamine, ethylenediamine, N-methylglucamine, and procaine (see, for example, Berge et al., “Pharmaceutical Salts,” J. Pharma Sci. 66, 1-19 (1977)). The base addition salts of said acidic compounds are prepared by contacting the free acid form with a sufficient amount of the desired base to produce the salt in the conventional manner. The free acid form may be regenerated by contacting the salt form with an acid and isolating the free acid in the conventional manner. The free acid forms differ from their respective salt forms somewhat in certain physical properties such as solubility in polar solvents, but otherwise the salts are equivalent to their respective free acid for purposes of the present invention.

Neuraxial, e.g., intrathecal or intraventricular, routes of administration may be preferred for certain applications (e.g. hyperalgesia), whereas oral dosing may also be applicable and is preferred for other applications (e.g., peripheral inflammation and pain). Compositions and formulations for intrathecal or intraventricular administration may include sterile aqueous solutions, emulsions and liposome-based formulations, which may also contain buffers, diluents and other suitable additives such as, but not limited to, penetration enhancers, carrier compounds and other pharmaceutically acceptable carriers or excipients.

The compositions of the present invention can comprise the usual non-toxic, pharmaceutically acceptable carriers for solutions, emulsions, suspensions, and any other form suitable for use. The carriers which can be used include glucose, lactose, mannose, gum acacia, gelatin, mannitol, starch paste, magnesium trisilicate, talc, corn starch, keratin, colloidal silica, potato starch, urea, medium chain length triglycerides, dextrans, and other carriers suitable for use in manufacturing preparations, in solid, semisolid, or liquid form. In addition auxiliary, stabilizing, thickening and coloring agents and perfumes may be used.

There are many enzymes and proteins that are homologous to cPLA₂ whose functions are less well known, such as GVI PLA₂, GIVB and GIVC. The common catalytic mechanism and divergent sequence homology of these enzymes makes them attractive co-targets along with cPLA₂. For example, inhibitors active against PLA₂ homologs which share a Ser-Asp active site with cPLA₂ and iPLA₂ may be co-administered with the PLA₂ inhibitors of the invention. Specific inhibition targets may, therefore, include Group IVB PLA₂, Group IVC PLA₂, Group VIA PLA₂, Group VIB PLA₂, neuropathy target esterase, phospholipase B (PLB's) from fungi, patatins in plants and various bacterial homologs such as ExoU from Pseudomonas aeruginosa (Phillips, R. M., Six, D. A., Dennis, E. A., and Ghosh, P., manuscript in preparation). The PLB's have been found to be critical for pathogenicity of fungi such as Candida albicans, and ExoU has also been found to be critical for cytotoxicity of a large percent of opportunistic Pseudomonas auruginosa.

Such homologs have various substrates, ranging from phospholipids to lysophospholipids to other ester-containing compounds. All, however, are related to cPLA₂ and to one another in their identical catalytic residues and catalytic mechanism. The invention therefore further encompasses co-administration of, or concurrent treatment with, inhibitors of PLA₂ homologs.

Data demonstrating the efficacy of the methods and compositions of the invention are provided in the Examples below. The examples shall not be construed as limiting the scope of the invention, which is defined by the appended claims. Abbreviations used in the Examples, such as “h” for hours, shall have their ordinary meanings.

The invention having been fully described, it will be readily apparent to those skilled in the relevant arts that other suitable modifications and adaptations to the methods and applications described herein may be made without departing from the scope of the invention or any embodiment thereof. It will therefore be understood that following examples are included herewith for purposes of illustration only and are not intended to be limiting of the invention.

EXAMPLE 1 General Methodology Utilized for Ex Vivo Experiments

Animals: Experiments were carried out according to protocols approved by the Institutional Animal Care Committee of University of California, San Diego. Male Holtzman Sprague-Dawley rats (250-350 g; Harlan Industries) were housed pair-wise in cages and maintained on a 12-hr light/dark cycle with free access to food and water at all times.

Intrathecal catheter implantation: For intrathecal drug delivery, chronic lumbar catheters were implanted in rats under isoflurane anesthesia according to a modification of the procedure described by Yaksh (Yaksh and Rudy, 1976). A polyethylene catheter (PE-10) was inserted through an incision in the atlanto-occipital membrane and advanced caudally to the rostral edge of the lumbar enlargement. Studies involving rats with chronic IT catheters were carried out 5 days after implantation, and rats were housed individually after implantation under the same conditions described above. Exclusion criteria were i) presence of any neurological sequel ii) 20% weight loss after implantation or iii) catheter occlusion.

Induction of inflammation and assessment of hyperalgesia: To induce a state of local inflammation, 2 mg of carrageenan (Sigma, St. Louis, Mo.; 100 μl of 20% solution (w/v) in physiological saline) was injected subcutaneously into the plantar surface of the left hind paw. To assess the thermally evoked paw-withdrawal response, a commercially available device was used, consisting of a glass surface (maintained at 25° C.) on which the rats were placed individually in Plexiglas cubicles (9×22×25 cm). The thermal nociceptive stimulus originates from a focused projection bulb positioned below the glass surface. The stimulus is delivered separately to either hind paw of each test subject with the aid of an angled mirror mounted on the stimulus source. A timer is actuated with the light source, and latency was defined as the time required for the paw to show a brisk withdrawal as detected by photodiode motion sensors that stopped the timer and terminated the stimulus.

Basal paw withdrawal latencies (PWL) were assessed at time (T)=−15 min. At T=−10 min the animals received intrathecal vehicle or drug and at T=0 the carrageenan was injected IPLT. Withdrawal latencies were then assessed at T+30, 60, 90, 120, 150, 180 and 240 min and expressed as the mean PWL of the left and right paws at each time point. The data was also presented as hyperalgesic index (HI). Hyperalgesic index is the percentage change from baseline averaged over each of the time points for the respective models. These values were cumulated [that is, the sum of (base line−postdrug latency)/(base line) divided by the number of measurements] so that increasing values indicate increasing hyperalgesia.

Formalin induced flinching. Flinching was assessed by an automated detection system. Using the system, a soft metal band (10 mm wide and 27 mm long, shaped into a C, and weighing ˜0.5 g) is placed on the hind paw of the animal being tested. The open part of the C is positioned at the top of the paw with the arms of the C gently compressed to form a bracelet around the paw. Animals are allowed to acclimate in individual Plexiglas chambers for 1 h before being moved to a test chamber. Just before the animal's placement into the test chamber, it is briefly restrained in a cloth towel, and 5% formalin (in volumes of 50 μl physiological saline) is injected into the dorsal side of the banded paw. Data collection is initiated after the animal is placed inside the test chamber.

Pain behavior was quantified by counting the incidences of spontaneous flinching or shaking of the injected paw. The flinches were counted for 1-min. periods for 60 minutes. Two phases of spontaneous flinching of the injected paw were observed after formalin injection and defined as phase 1 (0-9 min.) and phase 2 (10-60 min.). Upon completion of the 60-min observation, the rat was killed with pentobarbital sodium phenytoin sodium solution.

Drugs and Delivery. To examine the effects of drugs on carrageenan induced hyperalgesia and flinching behavior, rats received intrathecal or intraperitoneal injections of the drug. Intrathecal injections were done in rats that had been previously implanted with chronic intrathecal catheters (see above) using drug volumes of 10 μl followed by a 10-μl flush using vehicle. Intraperitoneal drugs were delivered in volumes of 0.5 ml/kg. AATFMK, MAFP and BEL (Cayman Chemical) were dissolved in DMSO (Sigma). The highest soluble dose was tested in regard to side effects in a pilot dose range study. The vehicle per se gave rise to an initial injection reaction in the form of scratching and vocalization that lasted for approximately 10 seconds. The drugs were well tolerated up to the highest soluble dose. No effect on normal behavior was observed except for BEL.

Tissue Preparation: Prior to sacrifice the rats were deeply anesthetized and after decapitation the spinal cords were ejected from the spinal column by a saline-filled syringe. The lumbar part of the spinal cord was frozen on dry ice and stored at −70° C. Frozen spinal cords were pulverized using a BioPulverizor (Biospec Products) pre-chilled on dry ice. Pulverized tissue was then transferred to a microcentrifuge tube and mixed with 750 μL lysis buffer: 10 mM Hepes, pH 7.5, 1 mM EDTA, 0.34M sucrose. 20 μL mammalian protease inhibitor cocktail (Sigma) was added immediately. Samples were vortexed and sonicated until homogenous and then centrifuged at 16,000×g, 4° C., 40 minutes. Supernatants were transferred to a fresh eppendorf tube and the pellet was discarded.

Western Blot: The protein concentration of the supernatant was determined by Bradford assay using BSA as the standard. 30 μg protein was run on a NuPAGE 4-12% Bis-Tris gel (Invitrogen) and then transferred to nitrocellulose. Protein was detected using an anti-human iPLA₂ antibody (a gift from Genetics Institute).

cDNA preparation: mRNA was extracted from supernatants using the TRIzol method (Gibco BRL) and contaminating DNA was eliminated by DNA-free treatment (Ambion) following the manufacturer's instructions. The concentration of the resulting DNA-free RNA was determined spectrophotometrically. cDNA was prepared using M-MLV reverse transcriptase (Gibco BRL) and oligo dT as the primer. Following cDNA preparation the samples were incubated with RNase H for 20 minutes at 37° C. to remove RNA.

PLA₂ gene fragment cloning: PLA₂ gene fragments were generated by PCR using the primers listed in the table below. The resulting fragments were purified from an agarose gel and cloned into the TOPO vector (Invitrogen). Each vector was sequenced to verify the identity of the insert and vector concentration was determined spectrophotometrically.

Q-PCR: Gene specific primers were designed using the Primer3 program (http://www-genome.wi.mit.edu/cgi-bin/primer/primer3.cgi/) or Primer Express 1.0 (Applied Biosystems). SYBR green was used to generate fluorescence for all genes tested except PLA₂ Groups IIA and V for which FAM probes were necessary to generate a single amplicon. Primer concentration and PCR conditions were optimized as described in the Applied Biosystems user bulletin and are listed below. Standard thermocycling conditions were used: 2 minutes at 50° C. UNG activation (for taqman chemistry), 10 minutes at 95° C. for polymerase activation, 40 cycles of 15 seconds at 95° C. and 1 minute at 60° C. Q-PCR results were analyzed by the standard curve method using untreated rat spinal cord to generate the standard curve. In the case of absolute quantification TOPO vector (Invitrogen) containing PLA₂ gene fragment inserts were used to generate the standard curve.

10 ng total cDNA was analyzed for each rat sample. GAPDH was used as the internal standard and acts as a loading control. Dissociation curves were generated following each Q-PCR run to verify the amplification of a single amplicon as is reccomended by Applied Biosystems. In the case of IIA and V where probes were utilized the PCR products were analyzed by agarose gel to verify the production of a single amplicon. PCR products were purified from gels and sequenced to confirm their identity. Primers, probes and PCR conditions are listed in the table below. Primer and probe concentrations listed are the final concentrations in the assay. [Primer] or Primer [Probe] Gene or Probe Sequence (nM) IB F Primer CTCCAAGGTCCCCTACAACA 500 R Primer GAAGTGGGGTGACAGCCTAA 500 IIA F Primer TGAACAAGAAGCCATACCACCAT 900 R Primer AGGAGGACCTTCATGCTGTCA 900 Probe CCCATCCAAGAGAGC 250 IIC F Primer CTCCACCCTACCCAGGTACA 500 R Primer AGCCTCTGGCATTGGTAGAA 500 IVA F Primer GACTTTTCTGCAAGGCCAAG 300 R Primer CTTCAATCCTTCCCGATCAA 300 V F Primer CCATCCGGACCCAGTCCTAT 300 R Primer CTTCCGGTCACAAGCACAAA 300 Probe TGCGAACACGACTCCTTCTGTCCAG 250 VI F Primer GCCTTCGCAGGTATCAAAAG 500 R Primer GGGAATCTGGTGAAAGTCCA 500 GAPDH F Primer ATGACTCTACCCACGGCAAG 300 R Primer GATCTCGCTCCTGGAAGATG 300

PLA₂ Activity Assays: Following homoginization and centrifugation, the spinal cord supernatants were assayed for cPLA₂ or iPLA₂ activity using the group specific assays developed in our laboratory (Yang et al., Biochem; 269: 278-288, 1999). Briefly the cPLA₂ assay conditions were: 100 μM lipid PAPC/PIP₂ (97/3) doping with 1% ¹⁴C labeled PAPC in 400 μM triton X-100 mixed micelles, 100 mM Hepes, pH 7.5, 0.08 mM CaCl₂, 0.1 mg/ml BSA and 2 mM DTT. iPLA₂ assay conditions were: 100 μM DPPC doping with 1% ¹⁴C labeled DPPC in 400 μM triton X-100 mixed micelles, 100 mM Hepes, pH 7.5, 5 mM EDTA, and 1 mM ATP. The total volume for each assay is 500 μL: 200 μL lipid, 250 μL assay buffer, 50 μL sample. In each case the amount of calcium or EDTA added was adjusted to account for the addition of EDTA in the lysis buffer to give the final concentrations listed above.

Lipid preparation: Lipid was dried under N₂ and lyopholized for at least one hour to remove all traces of chloroform. Lipid was then resuspended in 100 nM HEPES and triton X-100 and micelles were created by repeated vortexing and heating in hot water until the solution clarified. Samples were incubated with substrate for one hour at 40° C. The assay was then terminated and fatty acid extracted by the modified Dole assay. The amount of radioactive fatty acid released in the assay was determined by scintillation counting. Following analysis the data for the cPLA₂ assay was adjusted for contaminating iPLA₂ activity as described by Yang, et al. (Yang, et al., Anal. Biochem. 269: 278-288 (1999).

For the inhibitor studies the same phospholipid and buffer conditions were used as above with the addition of 4 μM or 0.8 mole % inhibitor. All commercial inhibitors were purchased from Cayman Chemical and their effectiveness was verified using pure GIVA or cell lysates known to contain iPLA₂ activity prior to assaying inhibitory effect in spinal homogenates. AAFTMK was incubated with homogenate for 4 hours prior to assay. MAFP and BEL were aliquoted into the lipid substrate immediately before the start of the assay.

Statistics Six to eight rats were included in each group for the formalin and carrageenan hyperalgesic measurements. Each timepoint and bar represents mean±SEM. Differences between groups were compared with one-way ANOVA using Statview statistical software. Three rats were included for each activity assay and PCR experiment. P-values were determined for the inhibitor assays using Graph Pad's on-line calculator.

EXAMPLE 2 Intrathecal PLA₂ Inhibitors Prevented Carrageenan-Induced Thermal Hyperalgesia

Carrageenan induces a characteristic inflammation and associated thermal hyperalgesia. Baseline latencies were assessed for all animals before injection of carrageenan and the average time to response was 11.1±0.4 seconds for the left hind paw (ipsilateral) and 10.6±0.7 seconds for the right hind paw (contralateral). After carrageenan injection into the plantar side of the left hind paw a reduction in time to paw withdrawal was detected. The withdrawal latency time decreased to 3.2±0.7 seconds at 120 minutes after carrageenan injection (FIG. 1A). There was no change of withdrawal time for either of the two control groups receiving IT saline or IT vehicle (data not shown). Pre-treatment with either IT AATFMK or IT MAFP resulted in a potent dose-dependent prevention of carrageenan-induced thermal hyperalgesia (FIGS. 1A and C).

Importantly, there were no changes in the response latency of the uninflamed paw even at the highest doses of either drug. A statistically significant reduction in the hyperalgesic index occurred upon administration of 200 μg IT AAFTMK (26±13) or 300/μg IT MAFP (25±11) in comparison with rats that received vehicle control (77±4) (FIGS. 1B and D). Because of limitations in solubility, the maximum dose given intrathecally differs between the two compounds.

There was a brief period of vocalization and scratching, approximately 10 seconds, following IT injection of the vehicle or the PLA₂ inhibitors. A test of spontaneous movement indicated that the compounds had no apparent effect on normal motor function (Table 1) although a third, iPLA₂ specific inhibitor (bromoenol lactone) did have such an effect as discussed in Example 4. To confirm that the antihyperalgesic effect of the intrathecally delivered PLA₂ inhibitors was due to spinal actions and not peripheral actions following redistribution from spinal to peripheral sites, the same amount of AATFMK (200 μg) that was given intrathecally was given intraperitoneally (IP). As shown in FIG. 2A no effect on the carrageenan-induced thermal hyperalgesia was seen following IP administration of 200 μg AAFTMK when compared to the control group that received IP vehicle.

Additionally the effect of intrathecal injection of AATFMK on carrageenan induced paw edema was assessed by measurement of paw height. The height of the ipsilateral paw increased significantly over the course of the experiment. The paw height peaked at 6 hours (FIG. 2B) and was back at baseline after 72 hours (data not shown). The contralateral paw did not show any signs of height increase and the PLA₂ inhibitor treatment did not have a statistically significant effect on the height of the carrageenan injected paw (FIG. 2B).

In order to examine the effect of the PLA₂ inhibitors on a state where thermal hyperalgesia is already established, AAFTMK was administered intrathecally 180 minutes after the carrageenan injection into the paw. In this study it was noted that, in comparison to pretreatment that fully prevented the onset on thermal hyperalgesia, posttreatment only partially reversed the hyperalgesia (FIG. 3).

To evaluate the anti-inflammatory activity of 2-oxoamide inhibitors, the rat carrageenan-induced paw edema assay was employed as a model for acute inflammation (reference drug indomethacin, 47% inhibition at 0.011 mmol/kg). The experiments were conducted on Fisher 344 female rats weighing 200-260 g. Acute anti-inflammatory activity was measured after 3.5 h by reduction of rat paw carrageenan edema, induced by injection of 0.1 mL carrageenan 2% (K100, commercially available) in sterilized saline intradermally into the right footpad. The examined compounds were administered intraperitoneally (ip) simultaneously. Control animals accepted only vehicle.

The acetic acid writhing test was used to assess the analgesic activity in rats (reference drug sodium acetylsalicylate, at 1 mmol/kg, 93.4%). The inhibitors were given ip and 30 min later 1 mL/100 g body weight of 0.6% acetic acid was given ip. After 5 min, the number of stretches were counted each 5 min for a period of 30 min. The total number of writhes exhibited by each animal in the group was recorded and compared to that of the vehicle treated control group.

The ED₅₀ values for 4-(2-oxohexadecanoylamino)-butyric acid (OA1) and (4S)-4-(2-oxododecanoylamino)-octanoic acid (OA4) were 0.01 mmol/kg and 0.1 mmol/kg, respectively. At a dose of 0.01 mmol/kg, corresponding to the ED₅₀ dose of the carrageenin paw edema test, 4-(2-oxohexadecanoylamino)-butyric acid (OA1) exhibited 92.7% analgesic activity. At a dose of 0.1 mmol/kg, corresponding to the ED₅₀ dose of the carrageenin paw edema test, (4S)-4-(2-oxododecanoylamino)-octanoic acid (OA4) exhibited 63% analgesic activity.

EXAMPLE 3 IT Administration of PLA₂ Inhibitors Suppressed Formalin-Induced Flinching

Injection of formalin into the dorsal side of the right hind paw evokes an initial burst of afferent input followed by a persistent low level discharge. This model predicts a biphasic increase in the activity of dorsal horn wide dynamic range neurons (Haley et al., Brain Res., 518218-226 (1990)) and a parallel biphasic appearance of flinching (FIG. 4) (Yaksh, et al., J. Appl. Physiol., 90: 2386-2402 (2001)). Pretreatment with AAFTMK and MAFP resulted in a dose-dependent reduction of the formalin induced flinching (FIGS. 4A, B and C). While Phase 1 was not significantly affected by the drugs, a statistically significant reduction was seen in Phase 2 (FIG. 4D) when compared to the group that received IT vehicle.

EXAMPLE 4 Intrathecal Injection of BEL, But not AATFMK and MAFP, Reduced Spontaneous Movement

In order to investigate the effect of the intrathecally administrated PLA₂ inhibitors on spontaneous movement the rats were placed on the flinch-counting device without receiving a paw formalin injection. The vehicle showed a tendency to reduce the number of counts although it did not meet statistical significance (Table 1, supra). The total number of counts generated over 60 minutes starting 10 minutes after IT injection of AATFMK or MAPF showed no statistically significant difference in comparison to the vehicle treated group. IT injection of BEL however, resulted in a measurable reduction of spontaneous movement (212±32 counts compared to 306±36 counts after vehicle injection) (Table 1, supra).

IT injection of BEL 10 minutes prior to paw formalin treatment resulted in suppression of formalin induced flinching (data not shown) but because of the reduction of spontaneous movement it is not possible to determine whether this effect is due to an antihyperalgesic effect or sedation/motor dysfunction. The effect of intrathecal BEL on hyperalgesic conditions was not further studied.

EXAMPLE 5 RNA Message for PLA₂ Groups IB, IIA, IIC, IVA, V and VI is Present in the Spinal Cord But is not Upregulated Following Injury

To determine the presence or absence of PLA₂ message in the spinal cord sequence specific primers were chosen to surround a splice junction for each rat PLA₂ gene available in the public database and RT-PCR was performed. Resulting fragments were then purified and sequenced to verify their identity. All PLA₂'s with sequences available in the public database were found to be present in the spinal cord with the exception of one (Group X).

To test for a possible upregulation in PLA₂ message following exposure to carrageenan, quantitative PCR (Q-PCR) was performed utilizing the primers used above. mRNA was extracted from non-treated rats or from rats either 2 hours or 4 hours following hind paw injection with carrageenan. cDNA was then made from the extracted mRNA. Changes in gene expression level were determined by Q-PCR using the standard curve method. Standard curves were constructed using cDNA from one of the control rats. GAPDH levels were determined by the same method and used as the internal reference.

Analysis by absolute quantitation (discussed below) indicated that no significant change in GAPDH levels occurred between control and treated animals. Following amplification, dissociation curves were generated or agarose gels were run for every sample to ensure specific amplification of a single amplicon. Analysis indicated that no upregulation of any of the PLA₂ genes following carrageenan injection occurred, as compared with control rats (FIG. 5).

Analysis by western blot also indicated that a stable level of iPLA₂ was maintained in control versus treated animals (FIG. 6). iPLA₂ has been reported to run at 60-65 kDa on SDS-PAGE. The larger band observed in FIG. 6 is likely dimerized enzyme as IPLA₂ is known to form oligomers through binding of its ankirin repeats.

The relative expression levels of the six PLA₂ genes were determined using the absolute quantitation method of Q-PCR. The gene fragments generated by PCR were cloned into the TOPO vector. The resulting circular DNA was then be quantitated by spectrophotometry and the copy number determined. These vectors were then serially diluted to have between 10,000 and 10 copies and Q-PCR was again performed on control rat samples using these vectors to generate the standard curves. Using this approach, it was confirmed that PLA₂ Groups IVA and VI are the predominant PLA₂ messages found in rat spinal cord.

EXAMPLE 6 Both cPLA₂ and iPLA₂ are Active in the Spinal Cord

Having found evidence for PLA₂ message and protein, the spinal cord was next tested for PLA₂ activity. Again analysis was performed on non-treated rats or carrageenan-treated rats either 2 hours or 4 hours following hind paw injection. Both cPLA₂ and iPLA₂ show significant activity in the spinal cord homogenates and no significant increase in activity was observed following carrageenan treatment (FIG. 7).

EXAMPLE 7 Ex Vivo Inhibition of cPLA₂ and iPLA₂ Activity in Macrophages

cPLA₂ and iPLA₂ are expressed in macrophage cells. It was therefore of interest to determine if the PLA₂ inhibitors of the invention acted on either or both of cPLA₂ and iPLA₂ in macrophages. To that end, P388D₁ murine macrophages were maintained at 37° C. in a humidified 10% CO₂ atmosphere. Cells were grown in Iscove's Modified Dulbecco's Medium (IMDM with 10% fetal calf serum (HyClone Labs, Provo Utah), 100 units/mL penicillin and 100 μg/mL streptomycin (Invitrogen, Carlsbad Calif.). Cells were routinely passaged every 2-3 days when the cells reached 75-80% confluence. Cells used for stimulation were plated at a density of 10⁶ cells per well in standard 12 well tissue culture plates and were allowed to adhere overnight.

Macrophages were stimulated by treating P338D₁ cells with either lipopolysaccharide (LPS) alone or LPS combined with platelet activating factor (PAF). Briefly, cells were washed twice with starvation media (IMDM containing 0.2% fetal calf serum, 100 units/mL penicillin and 100 μg/mL streptomycin) and then incubated with 1 mL of starvation media for one hour. Cells were then exposed to either 100 ng/mL LPS for 18 hours or 200 ng/mL LPS for one hour. Cells treated with 200 ng/mL LPS were then exposed to 100 nM PAF for 15 minutes. At the end of the stimulation, the media was removed from the cells, cleared of cellular debris by centrifugation and analyzed for prostaglandin E₂ (PGE₂) levels by enzyme-linked immunoassay (Cayman Chemical, Ann Arbor Mich.).

Inhibitor compounds were dissolved in DMSO and diluted into starvation media prior to addition to cells; the DMSO concentration was kept below 0.5% v/v in all studies. All inhibitors were added 30 minutes prior to stimulation.

Both OA1 and OA4 were tested in the LPS/PAF-stimulation conditions (FIG. 14). Both of these inhibitors showed essentially identical inhibition of the PGE₂ release from the cells. The inhibition reached close to 60% at the maximal dosage tested (50 μM). Thus, the data shown in FIG. 14 indicate that compounds OA1 and OA4 inhibit P388D₁ cPLA₂ under the LPS/PAF stimulation conditions, resulting in the partial abrogation of PGE₂ release.

Compounds OA1 and OA4 were also tested on the long-term LPS simulation conditions. As shown in FIG. 15, OA1 and were both able to completely block PGE₂ release with the addition of 50 μM inhibitor. Moreover, the data nicely fit to logarithmic functions and the IC₅₀ for the two inhibitors derived from these fits were 7.8 μM for OA1 and 5.8 μM for OA4.

EXAMPLE 8 Application of Synthesis Scheme to Production of Inhibitory Compound OA4

As a representative example of how the synthesis schemes for the inhibitory compounds of the invention may be applied, compound OA4 was synthesized as follows:

Benzyl(E,4S)-4-[(tert-butoxycarbonyl)amino]oct-2-enoate. To a solution of 2-(tert-butoxycarbonylamino)hexanol (0.22 g, 1.0 mmol), in a mixture of EtOAc/toluene 1:1 (6 mL), a solution of NaBr (0.12 g, 1.1 mmol) in water (0.5 mL) and subsequently AcNH-TEMPO (2 mg, 0.01 mmol) were added at −10° C. To the resulting biphasic system was added under vigorous stirring a solution of NaOCl (0.08 g, 1.1 mmol) and NaHCO₃ (0.08 g, 1.0 mmol) in H₂O (0.7 mL) dropwise at −10° C. over a period of 15 min. After stirring at −10° C. for 10 min EtOAc (15 mL) and water (5 mL) were added. The organic layer was washed with 1% aqueous citric acid (10 mL), which contained KI (0.5 g), 10% aqueous Na₂S₂O₃ (10 mL), brine and dried over Na₂SO₄. The solvent was evaporated under reduced pressure and the aldehyde was used directly to the next step without any purification.

To a solution of the aldehyde (0.21 g, 1.0 mmol) in dry THF (5 mL), Ph₃P═CHCOOBn (0.45 g, 1.1 mmol) was added and the reaction mixture was refluxed for 1 h. The solvent was evaporated under reduced pressure and the residue was purified by column chromatography (petroleum ether 40-60° C./EtOAc 9/1). Yield 0.22 g (65%); [α]_(D)−9.6 (c 1 CHCl₃); MS (FAB): m/z (%): 348 (5) [M+H⁺]; ¹H NMR: 7.36 (5H, m, C₆H₅), 6.90 (1H, dd, J=15.8 Hz, J=5.4 Hz, CH═CHCOO), 5.96 (1H, dd, J=15.8 Hz, J=1.4 Hz, CH═CHCOO), 5.18 (2H, s, CH₂C₆H₅), 4.51 (1H, d, J=7.8 Hz, NH), 4.28 (1H, m, CHNH), 1.62-1.17 (15H, m, 3×CH₂, C(CH₃)₃), 0.90 (3H, t, J=6.0 Hz, CH₃); ¹³C NMR: 166.4, 155.4, 149.6, 128.7, 128.5, 136.1, 120.4, 79.9, 66.5, 51.7, 34.6, 28.0, 22.6, 28.6, 14.1; Anal. Calcd. for C₂₀H₂₉NO₄: C, 69.14; H, 8.41; N, 4.03. Found: C, 69.05; H, 8.68; N, 3.84.

(E,4S)-1-(Benzyloxy)-1-oxooct-2-en-4-aminium chloride. Benzyl(E,4S)-4-[(tert-butoxycarbonyl)amino]oct-2-enoate (0.35 g, 1.0 mmol) was treated with 4 N HCl in Et₂O (8 mL) for 1 h at room temperature. The solvent and the excess acid were evaporated under reduced pressure and the residue was reevaporated twice from Et₂O. Yield 0.24 g (84%); [α]_(D) 10.8 (c 0.5 MeOH); mp 108-110° C.; ¹H NMR δ 7.35 (5H, m, C₆H₅), 6.92 (1H, dd, J=15.6 Hz, J=7.0 Hz, CH═CHCOO), 6.19 (1H, d, J=15.6 Hz, CH═CHCOO), 5.17 (2H, s, CH₂C₆H₅), 3.91 (1H, m, CHNH₃ ⁺), 1.85 (2H, m, CH₂CHNH₃ ⁺), 1.32 (4H, s, 2×CH₂), 0.88 (3H, t, J=6.0 Hz, CH₃); ¹³C NMR δ 165.1, 141.9, 128.6, 128.3, 135.4, 125.0, 66.5 (CH₂C₆H₅), 52.6, 32.5, 27.2, 22.0, 13.7.

Benzyl(E,4S)-4-[(2-hydroxydodecanoyl)amino]oct-2-enoate. To a stirred solution of 2-hydroxyhexadecanoic acid (0.54 g, 2.0 mmol) and (E,4S)-1-(benzyloxy)-1-oxooct-2-en-4-aminium chloride (0.28 g, 1.0 mmol) in CH₂Cl₂ (5 mL), Et₃N (0.3 mL) and subsequently WSCI (0.57 g, 3.0 mmol) and HOBt (0.32 g, 2.0 mmol) were added at 0° C. The reaction mixture was stirred for 1 h at 0° C. and at room temperature for 1 day. The organic layer was washed with brine, dried over Na₂SO₄ and evaporated under reduced pressure. The residue was purified by column chromatography (CHCl₃/MeOH 98/2). Yield 0.33 g (75%); [α]_(D)−10.3 (c 0.5 CHCl₃); MS (FAB): m/z (%): 446 (45) [M+H⁺]; ¹H NMR δ7.35 (5H, m, C₆H₅), 6.90 (1H, dd, J=15.6 Hz, J=5.4 Hz, CH═CHCOO), 6.65 (1H, m, NH), 5.92 (1H, dd, J=15.6 Hz, J=1.8 Hz, CH═CHCOO), 5.16 (2H, s, CH₂C₆H₅), 4.62 (1H, m, CHNH), 4.13 (1H, m, CHOH), 1.90-1.11 (24H, m, 12×CH₂), 0.88 (3H, t, J=6.0 Hz, CH₃); ¹³C NMR: 173.4, 166.0, 148.4, 128.6, 128.3, 135.7, 120.5, 72.2, 66.4, 49.5, 34.9, 34.7, 33.9, 31.9, 29.5, 29.3, 27.7, 25.0, 24.9, 22.6, 22.4, 22.3, 14.1, 13.8.

(4S)-4-[(2-Hydroxydodecanoyl)amino]octanoic acid. To a solution of benzyl (E,4S)-4-[(2-hydroxydodecanoyl)amino]oct-2-enoate (0.445 g, 1 mmol) in EtOH (2.5 mL), through which N₂ had been passed for 5 min, 10% Pd/C catalyst (0.042 g) was added. The reaction mixture was stirred under H₂ for 5 h at room temperature. The catalyst was removed by filtration through a pad of Celite and the filtrate was evaporated under reduced pressure. The product was purified by column chromatography (CHCl₃/MeOH 9/1). Yield 0.28 g (70%); mp 53-55° C.; [α]_(D)−2.4 (c 0.75 CHCl₃); ¹H NMR δ 6.82 (1H, m, NH), 4.18 (1H, m, CHNH), 3.91 (1H, m, CHOH), 2.39 (2H, t, J=6.3 Hz, CH₂COOH), 1.95-1.12 (26H, m, 13×CH₂), 0.88 (3H, t, J=6.0 Hz, CH₃); Anal. Calcd. for C₂₀H₃₉NO₄: C, 67.19; H, 10.99; N, 3.92. Found: C, 67.05; H, 11.18; N, 3.63.

(4S)-4-[(2-Oxododecanoyl)amino]octanoic acid (OA4). To a solution of (4S)-4-[(2-hydroxydodecanoyl)amino]octanoic acid (0.36 g, 1.0 mmol) in glacial acetic acid (4 mL), PDC (1.13 g, 3.0 mmol) was added. After stirring for 2 h at room temperature, the mixture was neutralized with 5% aqueous NaHCO₃ and extracted with EtOAc (20 mL×3). The combined organic layers were washed with brine solution and dried (Na₂SO₄). The solvent was evaporated under reduced pressure and the crude product was purified by column chromatography (petroleum ether 40-60° C./EtOAc 5/5).

Yield 0.20 g (57%); mp 50-52° C.; [α]_(D)−1.8 (c 0.5 CHCl₃); MS (FAB): m/z (%): 378 (35) [M+Na⁺], 356 (45) [M+H⁺]; ¹H NMR δ 6.86 (1H, d, J=9.4 Hz, NH), 3.90 (1H, m, CHNH), 2.90 (2H, t, J=7.8 Hz, CH₂COCO), 2.35 (2H, t, J=6.3 Hz, CH₂COOH), 2.01-1.05 (24H, m, 12×CH₂), 0.87 (3H, t, J=6.0 Hz, CH₃); ¹³C NMR: 199.4, 178.5, 160.1, 49.3, 36.8, 34.7, 31.8, 30.7, 29.8, 29.5, 29.4, 29.3, 29.2, 29.0, 27.9, 23.1, 22.6, 22.4, 14.1, 13.9; Anal. Calcd. for C₂₀H₃₇NO₄: C, 67.57; H, 10.49; N, 3.94. Found: C, 67.35; H, 10.77; N, 3.98

Other embodiments are within the following claims. In addition, where features or aspects of the invention are described in terms of Markush groups, those skilled in the art will recognize that the invention is also thereby described in terms of any individual member or subgroup of members of the Markush group.

The contents of the articles, patents, and patent applications, and all other documents and electronically available information mentioned or cited herein, are hereby incorporated by reference in their entirety to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. Applicants reserve the right to physically incorporate into this application any and all materials and information from any such articles, patents, patent applications, or other documents. 

1. A compound of the formula (1)

wherein R¹ is any acidic group, such as a carboxyl, phosphate, phosphinate, sulfate, sulfonate, or tetrazolyl group; R², R³ is any aromatic, heterocyclic, or carbocyclic group or a linear or branched, saturated or unsaturated alkyl, alkenyl, or alkynyl chain; n 0, m 0, k 0; its geometrical isomers, enantiomeric forms, pharmacologically or immunologically acceptable salts.
 2. The compound of formula (I) wherein k is >0 and one of m and n is >0.
 3. The compound according to claim 2, wherein k is 2-22.
 4. The compound according to any of claims 1-3, wherein R³ is methyl.
 5. The compound according to any of claims 1-4, wherein m is 0 and 3 and n is 1-12.
 6. The compound according to any of claims 1-4, wherein m is 3 and R² is CH₃.
 7. The compound according to any of claims 1-6, wherein n is
 3. 8. The compound according to any of claims 1-7, wherein R¹ is CO₂H.
 9. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising (4S)-4-[(2-oxododecanoyl)amino]octanoic acid, and a pharmaceutically acceptable carrier.
 10. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising 4-[(2-oxohexadecanoyl)amino]butanoic acid, and a pharmaceutically acceptable carrier.
 11. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising 4-[(2-oxooctanoyl)amino]butanoic acid, and a pharmaceutically acceptable carrier.
 12. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising (4R)-4-[(2-oxododecanoyl)amino]octanoic acid, and a pharmaceutically acceptable carrier.
 13. The compound of claim 1, further comprising a pharmaceutically acceptable carrier.
 14. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (II),

and a pharmaceutically acceptable carrier.
 15. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (III),

and a pharmaceutically acceptable carrier.
 16. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (IV),

and a pharmaceutically acceptable carrier.
 17. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (V),

and a pharmaceutically acceptable carrier.
 18. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (VI),

and a pharmaceutically acceptable carrier.
 19. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (VII),

and a pharmaceutically acceptable carrier.
 20. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (VIII),

and a pharmaceutically acceptable carrier.
 21. A pharmaceutical composition for use in inhibiting the enzymatic activity of phospholipase A₂ in a cell or organism, comprising the compound of formula (IX),

and a pharmaceutically acceptable carrier.
 22. A method for modulating the effects of inflammatory processes in a mammal, comprising administering an effective phospholipase A₂ inhibitory amount of one or more of the compounds according to any of claims 1-21.
 23. The method according to claim 22, wherein one of the effects of the inflammatory processes modulated is central nervous system inflammation.
 24. The method according to claim 22, wherein one of the effects of spinally mediated inflammatory processes modulated is prostaglandin E₂ production, wherein the prostaglandin E₂ production is reduced in response to treatment, compared to levels of prostaglandin E₂ production in the mammal prior to treatment.
 25. The method according to claim 22, wherein one of the effects of spinally mediated inflammatory processes modulated is pain, wherein pain perceived by the mammal is reduced in response to treatment, compared to levels of pain perceived prior to treatment.
 26. The method according to claim 22, wherein the inflammatory processes modulated are spinally mediated.
 27. The method according to claim 26, wherein one of the spinally mediated inflammatory processes modulated is hyperalgesia.
 28. The method according to claim 27, wherein the mammal is experiencing inflammation at one site in the body prior to treatment, and the pain perceived by the mammal prior to and following treatment is at another site in the body.
 29. The method according to claim 28, wherein the pain perceived by the mammal prior to and following treatment is at a site in the central nervous system.
 30. A method for modulating the effects of spinally mediated inflammatory processes in the central nervous system of a mammal, comprising administering an effective inhibitory amount of one or more inhibitors of phopholipase A₂ to the mammal.
 31. The method according to claim 30, wherein one of the effects of the spinally mediated inflammatory processes modulated is pain, wherein pain perceived by the mammal is reduced by inhibition of phospholipase A₂ activity, compared to levels of pain perceived prior to treatment.
 32. The method according to claim 30, wherein one of the effects of the spinally mediated inflammatory processes modulated is hyperalgesia, wherein inflammation experienced by the mammal is reduced by inhibition of phospholipase A₂ activity, compared to levels of inflammation experienced prior to treatment.
 33. The method according to claim 22 or claim 30, comprising neuraxial administration of the phospholipase A₂ inhibitor to the mammal.
 34. The method according to claim 22 or claim 30, further comprising administration of an inhibitor of one or more PLA₂ homologs to the mammal.
 35. The method according to claim 22 or claim 30, further comprising administration of a PLA₂ homolog inhibitor selected from the group of such homologs consisting of Group IVB PLA₂, Group IVC PLA₂, Group VIA PLA₂, Group VIB PLA₂, neuropathy target esterase, phospholipase B, patatins, and ExoU from Pseudomonas aeruginosa.
 36. A method for preparing 2-oxo-amide compounds, comprising synthesis of such compounds according to any one of synthesis Schemes 1-8.
 37. The method according to claim 36, further comprising modifying Scheme 1 to produce compounds having an amino acid side chain at R₂ selected from the α-, β-, γ-, δ-, or ε-forms of the amino acid.
 38. A compound for use in treating phospholipase A₂ mediated inflammation in a mammal, comprising a compound produced according to claim
 36. 39. A compound for use in treating phospholipase A₂ mediated inflammation in a mammal, comprising a compound produced according to claim
 37. 